1. Field of the Invention
The present invention relates to a vaccine formula allowing in particular the vaccination of pigs against reproductive and respiratory pathologies. It also relates to a corresponding method of vaccination.
2. Description of Related Art including Information Disclosed under 37 C.F.R. .sctn. 1.97 AND 37 C.F.R. .sctn. 1.98
During the past decades, the methods for the production of pigs have changed fundamentally. The intensive breeding in an enclosed space has become generalized with, as a corollary, the dramatic development of respiratory pathologies.
The range of symptoms of porcine respiratory pathology is in general grouped under the complex name of pig respiratory disease and involves a wide variety of pathogenic agents comprising viruses as well as bacteria and mycoplasmas.
The principal agents involved in the respiratory disorders are Actinobacillus pleuropneumoniae, the infertility and respiratory syndrome virus (PRRS) also called mysterious disease virus, the Aujeszky's disease virus (PRV) and the swine flu virus.
Other viruses cause reproductive disorders leading to abortions, mummifications of the fetus and infertility. The principal viruses are PRRS, the parvovirus and the conventional hog cholera virus (HCV). Secondarily, the swine flu virus PRV and A. pleuropneumoniae can also cause such disorders. Deaths may occur with A. pleuropneumoniae, HCV and PRV.
In addition, interactions between microorganisms are very important in the porcine respiratory complex. Indeed, most of the bacterial pathogens are habitual hosts of the nasopharangeal zones and of the tonsils in young animals. These pathogens, which are derived from the sows, are often inhaled by the young pigs during their first few hours of life, before the cholostral immunity has become effective. The organisms living in the upper respiratory tract may invade the lower tract when the respiratory defense mechanisms of the host are damaged by a precursor agent such as A. pleuropneumoniae or by viruses. The pulmonary invasion may be very rapid, in particular in the case of precursor pathogens such as A. pleuropneumoniae which produce potent cytotoxins capable of damaging the cilia of the respiratory epithelial cells and the alveolar macrophages.
Major viral infections, such as influenza, and respiratory coronavirus and Aujeszky's virus infections, may play a role in the pathogenicity of the respiratory complex, besides bacteria with respiratory tropism and mycoplasmas.
Finally, some agents have both a respiratory and a reproductive effect. Interactions may also occur from the point of view of the pathology of reproduction.
It therefore appears to be necessary to try to develop an effective prevention against the principal pathogenic agents involved in porcine reproductive and respiratory pathologies.
The associations developed so far were prepared from inactivated vaccines or live vaccines and, optionally, mixtures of such vaccines. Their development poses problems of compatibility between valencies and of stability. It is indeed necessary to ensure both the compatibility between the different vaccine valencies, whether from the point of view of the different antigens used from the point of view of the formulations themselves, especially in the case where both inactivated vaccines and live vaccines are combined. The problem of the conservation of such combined vaccines and also of their safety especially in the presence of an adjuvant also exists. These vaccines are in general quite expensive.
Patent applications WO-A-90 11092, WO-A-93 19183, WO-A-94 21797 and WO-A-95 20660 have made use of the recently developed technique of polynucleotide vaccines. It is known that these vaccines use a plasmid capable of expressing, in the host cells, the antigen inserted into the plasmid. All the routes of administration have been proposed (intraperitoneal, intravenous, intramuscular, transcutaneous, intradermal, mucosal and the like). Various vaccination means can also be used, such as DNA deposited at the surface of gold particles and projected so as to penetrate into the animals' skin (Tang et al., Nature, 356, 152-154, 1992) and liquid jet injectors which make it possible to transfect at the same time the skin, the muscle, the fatty tissues and the mammary tissues (Furth et al., Analytical Biochemistry, 205, 365-368, 1992). (See also U.S. Pat. Nos. 5,846,946, 5,620,896, 5,643,578, 5,580,589, 5,589,466, 5,693,622, and 5,703,055; Science, 259:1745-49, 1993; Robinson et al., seminars in IMMUNOLOGY, 9:271-83, 1997; Luke et al., J. Infect. Dis. 175(1):91-97, 1997; Norman et al., Vaccine, 15(8):801-803, 1997; Bourne et al., The Journal of Infectious Disease, 173:800-7, 1996; and, note that generally a plasmid for a vaccine or immunological composition can comprise DNA encoding an antigen operatively linked to regulatory sequences which control expression or expression and secretion of the antigen from a host cell, e.g., a mammalian cell; for instance, from upstream to downstream, DNA for a promoter, DNA for a eukaryotic leader peptide for secretion, DNA for the antigen, and DNA encoding a terminator.)
The polynucleotide vaccines may also use both naked DNAs and DNAs formulated, for example, inside cationic lipid liposomes.
M-F Le Potier et al., (Second International Symposium on the Eradication of Aujeszky's Disease (pseudorabies) Virus Aug. 6th to 8 th 1995 Copenhagen, Denmark) and M. Monteil et al., (Les Journees d'Animation Scientifique du Departement de Pathologie Animale [Scientific meeting organized by the department of animal pathology], INRA-ENV, Ecole Nationale Veterinaire, LYON, Dec. 13-14, 1994) have tried to vaccinate pigs against the Aujeszky's disease virus with the aid of a plasmid allowing the expression of the gD gene under the control of a strong promoter, the type 2 adenovirus major late promoter. In spite of a good antibody response level, no protection could be detected. Now, satisfactory results in the area of protection have been recorded after inoculation of pigs with a recombinant adenovirus into which the gD gene and the same promoter have been inserted, proving that the gD glcyoprotein could be sufficient for inducing protection in pigs.
The prior art gives no protective result in pigs by the polynucleotide vaccination method.